CHEMICAL WEED CONTROL IN NEWLY PLANTED RASPBERRIES IN COASTAL BRITISH COLUMBIA

Abstract

Over a 5-yr period (1980–1984) the efficacy of napropamide, simazine and terbacil applied singly and in mixture was investigated when applied to newly planted raspberries (Rubus idaeus L. ’Willamette’). Napropamide (4.48–8.97 kg/ha) gave less than satisfactory to good broadleaved weed control and excellent annual bluegrass and barnyard grass control. There was little improvement in efficacy with increased rate except when lady’s-thumb and shepherd’s-purse were the major weeds. Simazine (1.12–2.24 kg/ha) gave good to excellent broadleaved weed and grass control. Creeping yellow cress invaded the simazine-treated plots later in the season. Terbacil (0.67–2.24 kg/ha) generally gave good to excellent broadleaved weed and grass control except when common groundsel and pineappleweed were the major weeds. Significant year × herbicide × planting method interactions occurred on yields and plant vigor. Napropamide caused some reduction in the number of primocanes at emergence and some growth retardation. But, by late August, in all plots the primocane height was equal to or better than those in the control plots. First year fruit yields were not affected detrimentally. In 1 yr only (1980) primocane emergence from root cuttings initially was reduced by simazine at 2.24 kg/ha but not from dormant canes. There was no difference in primocane number or height by late August in any year. Yields were not affected. Again, depending on the year and rate, terbacil caused various degrees of injury from chlorosis to necrosis of new primocane growth. This injury was reflected in decreased yields in plants from root cuttings but not from dormant canes. Napropamide (1.1–2.2 kg/ha) in combination with simazine (0.6–1.1 kg/ha) or terbacil (0.34–0.67 kg/ha) showed considerable promise by the elimination of crop injury and the broadening of the weed control spectrum during early establishment of the raspberry plantation. There was no herbicide × planting method interaction for primocane height and number, although year effect was highly significant. Yields were equal to or greater than those from the control plants.Key words: Napropamide, simazine, terbacil, raspberry tolerance, raspberry, Rubus idaeus L.